何时使用依赖项属性 [英] When to use Dependency Properties

问题描述

我有时认为我可能不必要地使用了依赖项属性。我什么时候需要使用它？当我拥有一个依赖于其他属性的属性时？假设我有一个 Color 属性，我希望它依赖于属性色相，饱和度，亮度我是否使用依赖项属性？还是我用什么？我控制绑定到颜色的多数民众赞成在属性色相，饱和度，亮度更改时进行更新。

I sometimes think I maybe using Dependency Properties unnecessarily. When do I need to use it? When I have a property that dependes on other properties? Say I have a Color property that I want it to be dependent on properties Hue, Saturation, Luminosity do I use a dependency property? Or what do I use? I controls thats bound to Color to update when properties Hue, Saturation, Luminosity are changed.

目前我所做的是

public byte Hue {
    get { return _hue; }
    set
    {
        if (_hue == value)
            return;
        _hue = value;
        NotifyPropertyChanged("Hue");
        NotifyPropertyChanged("Color"); // to update controls bound to color
    }
}

但是我认为这不是正确的处事方式吗？如果我有更多影响颜色的属性，那么所有这些属性中都会有1条额外的行吗？

But I think this is not the right way of doing things? If I have more properties that affect color, I will have 1 extra line in all those properties?

推荐答案

您应该只使用一个 DependencyProperty 当您希望能够通过XAML将其值绑定到某项内容时，例如

You should only use a DependencyProperty when you want to be able to bind its value to something through XAML, e.g.

<local:MyObject MyDependencyProperty="{Binding ...}" />

更新：如以下Ian所述，如果要进行动画处理，还需要依赖项属性您的财产或通过样式进行设置

Update: as mentioned by Ian below, dependency properties are also required if you want to be able to animate your property or set it through a style

如果您不需要以这种方式工作，那就没有必要了。例如如果您只想通过XAML将值设置为常量（如下所示），则无需使用 DependencyProperty

If you do not need to work in this way then it is unnecessary. e.g. If you just want to be able to set the value to a constant through XAML (as below) this will work without using a DependencyProperty

<local:MyObject MyRegularProperty="Some Value" />

类似地，如果您想将绑定到 （例如）您的视图模型：

Similarly, if you want to bind to the value of a property on (for example) your view model:

<TextBlock Text="{Binding MyViewModelProperty}" />

然后，您不需要使用 DependencyProperty 。前提是您实现了 INotifyPropertyChanged ，则当属性更改时，文本仍将更新。

then you do not need to use a DependencyProperty. Provided that you implement INotifyPropertyChanged then the Text will still be updated when the property changes.

编辑：在重新阅读您的问题时，我不确定您是否使用 DependencyProperty来影响您的处境-如果我正确地阅读了它，那么您要做的就是在这些属性中的任何一个发生更改时，在UI上更新许多属性，对吗？

on re-reading your question, I am not sure whether or not your situation will be affected by whether or not you use a DependencyProperty - if I'm reading it correctly, all you want to do is cause a number of properties to be updated on the UI when any one of those properties changes, right?

我认为您目前的执行方式没有任何问题（即在每个设置器中引发很多 PropertyChanged 事件），但是如果您不热衷于此，则可以尝试使用一个单个属性来公开相关的子属性以进行绑定：

I don't think there is anything wrong with how you are implementing things at the moment (i.e. raising a lot of PropertyChanged events in each setter), but if you aren't keen on in then you could try having a single property that exposes relevant child properties to bind to that are all calculated:

class ColorWrapper
{
    public Color Color  { get; set; }
    public byte Hue
    {
        get { return this.Color.Hue; } //or however this is calculated
}

然后有一个 Color 属性引发 PropertyChanged 事件并通过View绑定到该事件：

Then have a Color property on your ViewModel that raises the PropertyChanged event and bind to that through the View:

<TextBlock Text="{Binding Color.Hue}" />

正如我所说，我不会说这是对您已经拥有的东西的特别改进

As I said, I wouldn't say that this is particularly an improvement on what you have already though.

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